1. Field of the Invention
This invention relates generally to control arms and to methods of making the same.
2. Related Art
Many automotive vehicles today employ suspension systems commonly known as MacPherson strut systems or double-wishbone systems. Such systems typically include a lower control arm (also referred to as an A-arm) which pivots relative to the vehicle's frame to allow a wheel and tire to move upwardly and downwardly relative to the frame during cornering or in response to encountering an object, such as a pot hole in the road.
A lower control arm 10 for a Macpherson strut type of suspension system is generally shown in FIG. 1. The lower control arm 10 includes a ball joint 12 for connection with a steering knuckle (not shown) of a hub assembly and a pair of bushings 14, 16 for guiding the pivoting movement of the lower control arm 10 relative to the vehicle's frame (not shown). One of the bushings is a horizontal bushing 14 which is configured to pivot relative to the vehicle frame about longitudinally extending bolt (not shown). The other bushing 16 is a vertical bushing which is configured to pivot relative to the vehicle frame about a vertically extending bolt (not shown).
Referring now to FIGS. 2A-C, an conventional vertical bushing 16 is generally shown. As best shown in FIG. 2C, the conventional vertical bushing 16 has an outer metallic sleeve 18, which is press fit into an opening in the lower control arm 10, a rubber cushion 20 and an inner metallic sleeve 22. The rubber cushion 20 extends radially between and interconnects the outer and inner metallic sleeves 18, 22. In operation, the inner metallic sleeve 22 pivots or twists relative to the outer metallic sleeve 18 during movement of the vehicle suspension, such as when the vehicle encounters a pot hole in the road. The rubber cushion 20 deforms elastically to allow the pivoting movement between these sleeves 18, 22 and absorbs/deforms due to a radial load. As such, during operation of the vehicle, the rubber cushion 20 is exposed to both a radial load and a twisting load motion. Exposure to the radial load and twisting motion leads to deterioration in the rubber cushion 20, thereby reducing the life of the vertical bushing 16.